Electronically encoding a digital password into a key is a well-known technique for enhancing the security of a mechanical locking device. However, such electronic security requires electrical power which must be supplied to both the key and the cylinder. The electronic components in the cylinder lock generally control a solenoid and significantly more power is required to activate this solenoid than is needed to power the key. As a result, the batteries that are needed for the cylinder are either prone to a short life or must be larger than is generally desirable. Since the power supply for the locking system is generally held in the key, which are carried by a person who will use the lock, this results in an undesirably large key.
Electronic locking mechanisms commonly use either linear or rotary actuators to complete the final element of the unlocking process once a code on a key has been matched with the code held on the lock. When a design relies upon power being delivered to a linear actuator power needs to be supplied for a considerable amount of time, often several seconds to ensure the lock remains unlocked until the key is turned. Where a design uses a rotary actuator some means has to be provided to cause the actuator to rotate in the opposite direction in order to relock once the key has been removed (which also removes the power supply). Unless there are sensors in the lock there is no way of knowing if the rotary actuator has properly reset. This is a fundamental weakness in some electronic locks. When they sense that the key has been removed, energy stored in on board capacitors (charged from the key) drives a tiny motor. However, many such locks have no sensors so have no way of knowing if the lock has reset. The only way of telling is to insert a correct mechanical key without electronics. If it still unlocks, the lock has not properly reset. An alternative to this is to use a separate feature on the key to cause a reset during key removal. However, removal of the feature means the reset will not work and any key will then open the lock.
In mechanical locks it is known to use magnets to control the locking process. However, locating a magnet on a key is undesirable as the magnet may affect close by located objects such as the magnetic strips on machine-readable cards such as credit cards. Furthermore, the magnet will attract small and microscopic pieces of ferromagnetic material which may then be dislodged from the key in a lock mechanism potentially resulting in fouling of the mechanism.